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Geo thermal heat pumps

Post in 'The Green Room' started by karl, Jun 15, 2008.

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  1. Redox

    Redox Minister of Fire

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    Since the typical well is 4" diameter and the pump is just a shade smaller than that, it would be impossible to get a loop down past the pump. I also think you could wind up with a mess if you dropped a loop in without some kind of support system. This is uncharted territory AFAIK and may have other problems such as cross contamination should the heat pump loop develop a leak. I'm not sure I would want to be the guinea pig...

    I can definitely understand the desire to completely cut yourself off from the oil barons, but installing a full zoot heat pump for only occasional use doesn't seem like it would pay back very fast, IMHO. The system you have is already paid for and probably works well enough for the few times you would need it. If it is having problems, then you might want to explore less expensive options, as you aren't going to be using it all that much.

    Just my$.02

    Chris

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  2. Jerry_NJ

    Jerry_NJ Minister of Fire

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    Only closed loop systems are legal in NJ. This was true even 15+ years ago when mine was installed. I also have a well for water, best I recall a the moment it is about 125' deep, so my closed loop heat exchangers (two loops) at 250 feet spend a lot of time in water (not dirt) and that should go a long way to keep the loop temperature on the return side near geothermal (ground) temperature/well-water the desired result. I can say my circulation pumps don't use a lot of power, mine is two stage at the circulation level too, but they look heavy duty, are sizeable. The two stage circulation pump is part of the maximize economy strategy, when the compressor is running on low speed, the HP is using the lower power setting for pumping the closed loop too.
  3. Redox

    Redox Minister of Fire

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    I thought the wells were supposed to be packed with mud or bentonite or something...

    Chris
  4. Wet1

    Wet1 Minister of Fire

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    I was just reading over this thread with casual educational interest and it reminded me about the two unused wells I have on my property (both within 60' of my house). I live very close to the ocean so the ground below the topsoil is mostly sand and the water table is high, probably within 5'-8'. It might even be higher than this as all my neighbors have sump pumps running from spring through fall. We now have city water so the wells aren't used, but they always have water in them. They both have cement slabs covering them and each is several feet in internal diameter and of unknown depth.

    Would/could there be any value of using these for heating or cooling? Ideas???
  5. mbcijim

    mbcijim Member

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    Geothermal Pricing (GSHP) -

    I am building a new house as we speak. I received two prices (May 2008), at about the same price. $23,000 + ground loop excavation (self performed).
    This is for 7 tons (2 units 1# 5 ton, 1# 2 ton), hot water, and ductwork (hot air system). The house is 3,200 sft plus a basment of 2,200 sft. The entire house is conditioned. This is eastern rural PA. I've spoken to two families in the same area as me with about the same size new house and a GSHP Neither electric bill has ever exceeded $200.

    My HVAC contractor says that all I am saving energy wise over an air exchange Heat Pump is a 1/2 HP pump. Without a doubt, an air exchange heat pump is a better return on your investment. The savings to go to ground source probably don't justify ground source. I have the $, I'm 32, and plan on living in the house for a long time, so I did it. I am looking at the very long term picture and could justify the additional money.

    If you want cheap heat, go for coal or wood. They both have less $/BTU cost, but both involve work. It is cheaper than wood pellets, corn, and just about everything else. I wanted the cheapest heat with no work.
  6. Jerry_NJ

    Jerry_NJ Minister of Fire

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    I don't understand you HVAC contractors comment about a 1/2 hp pump. At temperatures below 30 degrees the Geo will save a lot more over an air-to-air than the energy used by a 1/2 hp pump. Same for A/C when the air temps are in the 90s. Both of these exist often in eastern PA, and central/western NJ where I live. I don't understand the not over $200 either, for a 3,200 SqFt home, plus basement. I have a 2,000 SqFt home plus basement and I saw bills nearing $300 for February. Electricity in PA may be lower cost than NJ, but I'll bet not 30% less expensive.
  7. mbcijim

    mbcijim Member

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    I think his comment about the 1/2 HP pump meant if you look at the two units side by side that is the difference. You make a good point about air temps though, you're right about that.

    Hopefully the $200/month people aren't lying to me! I am just repeating what they said. Are you saying you have a GSHP and it cost you $300/month? PA's electric cost is about $.12/KW.
  8. Jerry_NJ

    Jerry_NJ Minister of Fire

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    Right, the difference is the pump, in my system two pumps (two speeds, runs in low as long as it can to increase efficiency) to circulate liquid in the ground loop..and that's another difference, the ground loop.

    I had only one month last winter near $300, maybe it was $279, I was just estimating against the $200 number. I was paying 15 cents per KWH, so that's part of the reason for a higher cost at my end. Still, I have onlly 2,000 sqft and that's a two story with an "all electric" construction (circa 1985). We have R38 in the ceiling and R19 in the walls.
  9. Highbeam

    Highbeam Minister of Fire

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    Perhaps the 200$ was their annual average. I can appreciate the concept of a no-work source of heat but also greatly appreciate the value of an additional alternative source that is independent of electricity even if it includes some work. I wish we had a heat pump of ground or air source.

    The installs into vertical wells that I've read about all included a bentonite or other fill of the well around the geo loop to ensure good contact with the earth for thermal transfer. You can depend on the ground to be there but the water level may drop and leave your geoloop in the air. People have also been known to use ponds as a thermal sink and just lay loops of poly geo loop in the pond. Imagine that, in the summer, your home's AC load is actually heating the pond for swimming.
  10. Jerry_NJ

    Jerry_NJ Minister of Fire

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    Yes, there was some fill in my vertical loops, and my contract didn't include cleaning up the stuff pulled out of the holes while drilling. How much can that be for two holes? A lot, it took a lot of work to remove the "slag" from my property, actually I just moved it to a hill side on my property.

    The really great thing about A/C is the waste heat, if you can capture it for your hot water needs, bingo, free hot water. My system has a high temperature loop that feeds in/out of my existing water heater through the drain tap, bad news: the dual use of the one 1/2" hole (I'm estimating the size, coule be 3/4") is the water channels are so narrow that they get stopped up easily, and have, I no longer try to use. So, no FREE hot water for me. A simple auxiliary tank with a dedicated and separate in/out would fix the problem. I don't know if the HP or A/C suppliers have such a offer. Keep in mind, one doesn't need a heat pump for this, as the only time you have throw-away heat is when A/C is running.
  11. Redox

    Redox Minister of Fire

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    The difference is a lot more than the pump. First off, you will not need an outdoor fan motor. Air source units will probably have anything from 1/10 to 1/4 hp fan on the outdoor unit. The pump will probably be bigger than that, but the real savings comes from the differing temperatures on the water side. Since the earth moderates the temperature, there will be a smaller temperature difference and this delta T is the primary governing factor in efficiency in a refrigeration system. There is also no defrost cycle on a GSHP which kills your efficiency in the winter as the humidity goes up and the temperature goes down.

    You will need the same size circuit to start that compressor, but the running amps will be much lower on a GSHP because the compressor isn't working as hard. You will also need a pretty serious generator if you want to use one in a power failure, if that is a consideration. The $200-300 bills mentioned here would seem to jibe with what I am hearing for our climate. If you want the most efficient system available, go ground source. If you aren't going to be using it 24/7 or don't need a lot of A/C, air source is simpler and significantly cheaper. As the price goes up, so does efficiency, but spending twice as much on a heat pump will probably not cut your bill in half and will likely cost more if it breaks.

    You can heat water with a heat pump with a device called a desuperheater. It is nothing more than a heat exchanger and a small circulator that cools the hot gas as it leaves the compressor regardless of whether you are heating or cooling. This option is common on GSHPs but I don't think I've ever seen one factory installed on a regular heat pump or A/C. They can be added, but it requires breaking into the refrigeration system and will probably void a warranty if it exists. They are almost "free" in the cooling mode, but are stealing heat in the winter. They work best when they are installed as a preheat system similar to a solar water heater. I haven't seen a whole lot of them around as they make more sense in southern climates where you are running the A/C more. I'm still waiting for someone to come out with a dedicated water heating heat pump. So far, all I've been able to find is a little fractional horsepower job that cools the basement:

    http://www.aers.com/etech_residential_water_heating.html

    BTW, anybody know what it costs to drill a well these days?

    Chris
  12. mbcijim

    mbcijim Member

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    Thank you guys for correcting my comments on just the fan difference. I'm thinking my HVAC guy is feeding me a line of BS. Anyway, I'm committed to GSHP at this point. I did already buy a Summit Classic for the house for backup, and maybe a hobby! I love sitting around a wood stove in the winter...
  13. Jerry_NJ

    Jerry_NJ Minister of Fire

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    While talking about geothermal, my experience suggests the efficiency for heating verses cooling isn't symmetrical/equal. Absent any measurement, and I suppose the BTU specification for heating and cooling should tell the story, I may dig out the specs next, it seems to me I get more BTUs per dollar heating over cooling.

    Here's what made me think about it, were on A/C now and I'd say the outside temperature is about 90 degrees, inside about 75 degrees. It seems to me the A/C is running a good bit and I expect an electric bill in the neighborhood of what I get in the winter when I"m heating to 65 degrees and the outside temperature is about 30 degrees. My point? It seems to me it cost me as much to take 15 degrees off in the summer as it does to add 35 degrees in the winter. It can't be the insulation, it works both ways...maybe the sun is part of the answer. In th winter the house gets full southern exposure and this helps warm the house. In the summer I get some shade to help shield the house, but the house still gets some warming from the sun hitting the house. In addition, we pay about 15% more for electricity in the summer, I suppose about 18 cents per KWH this summer.
  14. Redox

    Redox Minister of Fire

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    That difference is due to the heat of the motor/compressor. In the winter, this heat is a benefit and is roughly equal to electric resistance heat on top of the heat from the refrigeration effect. In the summer, this is just waste heat and needs to be rejected along with the refrigeration heat.

    Heat pumps also draw more current in the cooling mode than when heating, but the difference is smaller on water source. You noticed that most utilities charge more per kw in the summer but also consider that most homes are self heating due to internal gains from lights and appliances. Humans also emit heat and humidity as well and this is more noticeable in the summer.

    Chris
  15. syd3006

    syd3006 Member

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    I am in the process of having a "ground source heat pump" installed. The price for everything installed not including electrical or duct-work is $15700.00 and change. This is a 4 ton unit with electric backup and provisions for heating my hot water. The provincial and federal governments will reimburse me $3500 each for a total of $7000.00. I am required to have an inspection of my house which basically tells how energy efficient it is. The inspector seals off a door and then installs a fan type gadget which he gradually restricts the air flow through and this tells him how much air or heat loss I have. For this inspection I paid $315.00 of which the government will reimburse $150.00. Once everything has been installed and is up and running I have to get another inspection which I will have to pay another $300.00 for. If all goes as it is supposed to I will get all my rebate cheques within 90 days.
  16. Redox

    Redox Minister of Fire

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    That sounds like a good deal to me! Does this price include wells or loop installation? How big and how old is the house? I hate to be a pest, but I like details.

    Thanks,
    Chris
  17. Jerry_NJ

    Jerry_NJ Minister of Fire

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    Sounds like a great price (what is the mfg for the heat pump?) to me. I paid about $12K for a 4 ton unit installed as a replacement for an air-to-air. Of this about $4K was for the ground loops, two 500' vertical loops or 2K feet at an average depth of 250', in the water aquifer most of the distance. I got a $3K rebate from the power company, with the larger rebate you quote, your price is no more than mine was in 1994, surprising.

    I do recall a lower cost unit back when I was shopping that directly buried the heat exchanger, big coil of copper pipe so there was less digging, less cost. I didn't like the design, but can say it did qualify for the power company rebate, so their engineers thought it was ok efficiency-wise.
  18. syd3006

    syd3006 Member

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    Yes the price includes the installation of the ground loop, I have it in already, I'm just waiting for the rest of the system to be installed. As far as the grant goes I don't think the size or age of the house has a bearing as long as you are converting to one of the energy efficient systems they approve. My house is 1056 square feet and was built in 1978. The name of the company that makes the "Heat pump" is "Hydron" they are located in Mitchell, South Dakota.
  19. Jerry_NJ

    Jerry_NJ Minister of Fire

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    I found the Hydron web site a bit difficult to read, but found one good reference: http://www.ari.org for independent specs on HPs, and other compressor gear. I didn't see Hydron on the ARI site.

    The Hydron site listings left me with the conclusion that it is supplied only as an open loop system, is that right? We can not run open loop, so if I should outlive my existing geothermal I'll not be able to consider Hydron as a replacement. The COP suggested, 3.5, in one of the Hydron listings isn't quite as high as my two speed Waterfurnace HP, it is rated at 4.3 in low speed with a loop temp of 32 degrees F. Of course that's a limit and I expect to get better under most conditions as the loop is usually way above 32 degrees, more likely in the 40s. My loop has antifreeze so it can run below freezing for water.
  20. Redox

    Redox Minister of Fire

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    I hate to be throwing questions this late in the game at you, but has anyone done a heat load calculation on your house? 4 tons sounds like an awful lot of compressor for 1000 SF.

    Chris
  21. Jerry_NJ

    Jerry_NJ Minister of Fire

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    I think NW Ontario may need more BTUs for heating. My 4 ton is for 2,000 sq ft, two story built for all electric and worse case 0 degrees outside. At the design limits the 4 ton heating will require at least periodic cut in of resistive heat, it has two stages of that, which also serves as emergency heat. In any case, I agree 4 tons sounds like too much for 1056 sq ft, but maybe not for Ontario.
  22. Highbeam

    Highbeam Minister of Fire

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    And not in 1978.
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